1. Field of the Invention
The present invention relates generally to light modulators, and more particularly but not exclusively to micro electromechanical system (MEMS) based spatial light modulators.
2. Description of the Background Art
Spatial Light modulators fabricated using micro electromechanical system (MEMS) technology, in general, are well known. Examples of such light modulators include the Grating Light Valve™ (GLV™) light modulator available from Silicon Light Machines Corporation of Sunnyvale, Calif. Devices that are of the same type as GLV™ light modulators are hereinafter referred to as “ribbon light modulators”. Ribbon light modulators are described in the following disclosures, which are integral to this provisional application and can be found in the following patents: U.S. Pat. No. 5,311,360, entitled “Method and Apparatus for Modulating a Light Beam” to Bloom et al.; U.S. Pat. No. 5,841,579, entitled “Flat Diffraction Grating Light Valve” to Bloom et al.; U.S. Pat. No. 5,661,592, “Method of Making and an Apparatus for a Flat Diffraction Grating Light Valve” to Bornstein et al.; and U.S. Pat. No. 6,215,579, entitled “Method and Apparatus for Modulating an Incident Beam for Forming a Two-Dimensional Image” to Bloom et al. The aforementioned four U.S. patents are hereby incorporated by reference. Ribbon light modulators can be employed in various applications including optical networks, video, and printing.
FIGS. 1 and 2 show schematic diagrams of conventional ribbon light modulator structures. In FIG. 1, each ribbon 102 with reflective layer 103 is electro-statically deflectable towards the substrate 104, with reflective layer 106 thereon, to form a diffraction grating with adjustable diffraction strength. In FIG. 2, active deflectable ribbons 202 are interlaced with static un-deflectable ribbons 204 also to form an addressable diffraction grating with adjustable diffraction strength. In FIG. 2, the substrate 208 need not have a reflective surface layer. A ribbon 102 and a gap 108 (ribbon-gap) pair 110 in FIG. 1 or an active ribbon 202 and a static ribbon 204 (ribbon-ribbon) pair 206 in FIG. 2 constitutes a diffraction period. One or more periods can be addressed as a “pixel.” A pixel can be addressed to modulate incident light by diffraction. Thus, a pixel can be used to display or print a unit of an image, for example.
While conventional spatial light modulators can be satisfactorily used in a wide variety of high resolution applications, there are emerging applications that may require even higher pixel resolution. Examples of these emerging applications include super high resolution display, maskless lithography, high resolution printing for printed circuit boards and flat panel displays, and a host of other applications. There are also existing applications, such as laser printers, that can be considerably improved by the use of high resolution spatial light modulators.